Seems to me that for what you need the computer for, you could go with last year's models and will be able to tell no difference.
The kind of performance boosts that these releases offer are really only noticeable to people who actually benefit from them using professional high demanding applications.
For browsing the web, listening to music, sending emails and using Microsoft Office these "improvements" are meaningless. RAM is probably the thing that will make your computer run faster irrespective of CPU and graphics card models.
So if you want to wait wait...it's always "nice" to have the latest and greatest even if it really makes no difference to an average computer user--you can get a 2 year old computer (stocked with enough RAM of course) and you will see no difference. Another reason to upgrade is of course changes in the computer's features outside of performance...better screen, better trackpads, lighter, battery improvements etc etc. Those come gradually as we all know, a 2 year old Core Duo MBP is significantly inferior in those respects, so even if the performance changes nothing for the average non-pro user, the computer itself has improved a lot.
Ultimately the MacBook Pro line was recently overhauled after many years design wise going back to the PowerBook days...the current line is going to stay as is or refined very gradually over time like the last models for a very long time. The next crop of processors will not bring with them radical design changes...the changes already took place a year ago. So if you want to wait for Apple to do something with the computer at the next update besides the new chips you will probably be disappointed.